1. Field
Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to techniques for managing simultaneous unicast and multicast/broadcast services in such systems.
2. Background
Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, etc. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Examples of such multiple-access networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.
A wireless communication network may include a number of base stations that can support communication for a number of user equipments (UEs). A UE may communicate with a base station via the downlink and uplink. The downlink (or forward link) refers to the communication link from the base station to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the base station.
In a wireless communication system, a UE may communicate using a dedicated unicast service that provides two-way point-to-point communication between the UE and the network. Such a unicast service may occur at various transmission rates that are either defined or negotiated at some point in time after the UE is recognized by the system. Another commonly available communication service, which supports a one-to-many arrangement, has come to be known generally as a broadcast service. One of the commonly defined and accepted broadcast communication services is known as Multimedia Broadcast/Multicast Service (MBMS). In the context of 3GPP Long Term Evolution (LTE) systems, such a service is known as Evolved Multimedia Broadcasat/Multicast Service (eMBMS or E-MBMS).
Simultaneous support for unicast and eMBMS services in a UE presents some challenges. One challenge is that whether to support the two services simultaneously is an implementation choice left to the UE designer, and not all UEs support the two services simultaneously. This means the UE has to choose between the two services when presented with an opportunity to support both. A UE that cannot support both services simultaneously may choose, for example, to prioritize an eMBMS service over a unicast service. At least two problems can arise in such a case: (1) the UE may miss important unicast traffic while it is receiving eMBMS traffic and (2) it may take time for an eNodeB (base station) to figure out that the UE has autonomously disconnected from unicast service in favor of an eMBMS service, resulting in inefficiency.
Another challenge associated with providing simultaneous unicast and eMBMS services in a UE is that, even if the UE supports the two services simultaneously, a modification of the transmission parameters of one of the services (typically the unicast service) may be required to permit the UE to support both services simultaneously. For example, a particular UE might need to receive unicast traffic at a lower data rate to permit an eMBMS service to continue without disruption. Some current designs attempt to solve this problem by allowing the UE to update its capabilities with the network through the sending of an unsolicited UE capability information message on an as-needed basis. Though this helps the UE to support simultaneous unicast and eMBMS services, it complicates standard-compliance certification testing because of the additional uncertainty it introduces.